N4 Session Modification Call Flow

N4 Session Modification is used to update the N4 session context of an existing PDU session at the UPF, which is executed between SMF and UPF whenever PDU session-related parameters have to be modified.

StepDescription
1SMF receives the trigger to modify the existing PDU session.
2SMF sends an N4 session modification request message to the UPF which contains the update for the structured control information that defines how the UPF needs to behave.
3UPF identifies the N4 session context to be modified by the N4 session ID and updates the parameters of this N4 session context according to the list of parameters that are sent by the SMF. UPF responds with an N4 session modification response message containing any information that the UPF has to provide to the SMF in response to the control information received.
4SMF interacts with the network entity which triggered this procedure. For example, AMF or PCF.